JP2000221776A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make an excellent image so as possible to be formed by maintaining a fine thin layer on a developing roller, without being disturbed by the change in aggregation of toner with age. SOLUTION: This developing device is, allowed to apply a specified bias voltage by bias applying means 41 and 43, with regard to a blade 26C that is thin layer member so as to generate a specific potential difference between the developing roller 23C, and to variably control the above potential difference in accordance with the change of the aggregation degree of the one component developer, by the voltage variable device 42 that is bias variably controlling means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for developing a latent image on an image carrier with a one-component developer, for use in an image forming apparatus such as an electrophotographic copying machine, a printer, a facsimile, and a multifunction machine thereof. Related to the device.

[0002]

2. Description of the Related Art JP-A-6-194944 has a supply roller for supplying toner to a developing roller.
There is disclosed a technology in which a bias voltage applied to a supply roller is variably controlled in accordance with a change in physical properties of a supply roller in a developing device of a one-component development system in which a predetermined bias voltage is applied to each of them.

As described in this publication, a developing device of a one-component developing system is advantageous in simplifying and downsizing an image forming apparatus, but imparts charge to toner and transports the toner onto a developing roller. Since there is no carrier, the chargeability (rise) of the toner and the transportability (conveyance amount) of the toner are inferior to those of the two-component developing system.

[0004] Therefore, according to the technology described in this publication, when the amount of toner transported is smaller than the amount of toner consumed during development, a phenomenon of a decrease in image density on a printed image is observed. The toner is improved in fluidity to prevent packing due to false solidification after standing. Since the fluidity is improved, it is difficult to reduce the thickness of the toner on the developing roller, and there is a possibility that the image may be omitted due to a defective thin layer. It has been confirmed that this thin layer defect does not occur when the fluidity of the toner decreases over time.

The present invention has been made in view of the above background. A first object of the present invention is to maintain a good thin layer on a developing roller without being hindered by a change in the degree of aggregation of toner over time. Another object of the present invention is to provide a developing device on which a complex image is formed.

A second object is to maintain a good image with a simple structure such as counting the number of latent image formations by previously determining the relationship between the reduction in the degree of aggregation of toner, the number of latent image formations, and image blanking. Is to be able to do it.

A third object is to form a toner image on an image carrier and directly detect the white spot of the toner image by the toner image adhesion state detecting means, thereby more reliably detecting the white spot and improving the image quality. The purpose of the present invention is to maintain a proper image.

[0008]

SUMMARY OF THE INVENTION In order to achieve the first object, the present invention is directed to a method for forming a latent image on an image carrier using a one-component developer carried on the surface of the image carrier. A developing device comprising: a developing roller for developing; a thin layer member for thinning a one-component developer on the developing roller; and first bias applying means for applying a predetermined developing bias voltage to the developing roller A second bias applying means for applying a predetermined bias voltage so that a predetermined potential difference is generated between the thin layer member and the developing roller, and the potential difference is determined according to a change in the cohesion degree of the one-component developer. Bias control means for variably controlling the bias voltage.

In order to achieve the second object, the variable bias control means variably controls the potential difference in accordance with the number of latent images formed on the image carrier.

Further, in order to achieve the third object, a one-component developer for forming a latent image as a measurement pattern on an image carrier and detecting a state of one-component developer adhesion to the latent image as the measurement pattern. An agent adhesion state detecting means is provided. Then, the variable bias control means is configured to variably control the potential difference according to the measurement result of the one-component developer adhesion state detecting means.

[0011]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show a schematic structure of the entire inside of a color image forming apparatus provided with a color developing device according to the present invention. FIG. FIG. 2 shows this in an open state.

In FIG. 1, a flexible photoreceptor belt 1 serving as an image carrier is provided between rotating rollers 2 and 3 and is driven in the direction of arrow A (clockwise) in FIG. Conveyed. The surface of the photoreceptor belt 1 is uniformly charged by a charging charger 4 as charging means and is exposed by a laser writing unit 5 as electrostatic image exposure means. Then, the yellow, magenta, cyan, and black developers (toners) are produced by the color developing device 6 according to the present invention.
Is developed for each color by four developing devices each having

An intermediate transfer belt 10 serving as an intermediate transfer member is provided.
Is provided between the rotating rollers 11 and 12, and is conveyed in the direction of arrow B (counterclockwise) in the figure by the rotation of the rotating roller 11. The photoreceptor belt 1 and the intermediate transfer belt 10
The rotation roller 3 of the photoreceptor belt 1 is in contact therewith. A bias roller 13 having conductivity is in contact with the back surface of the intermediate transfer belt 10 on a predetermined condition on the intermediate transfer belt 10 side of the contact portion.

Next, an image forming operation of the color image forming apparatus will be described. Referring to FIG.
Is uniformly charged by the charging charger 4 and is then scanned and exposed by the laser writing unit 5 based on image information to form an electrostatic latent image on the surface. Here, the image information to be exposed is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information, and a laser beam generated by a semiconductor laser (not shown) based on this information. L is scanned and optical path adjusted by an optical device not shown.

The electrostatic latent image formed here is developed in a single color by yellow, cyan, magenta, and black toners by four developing units of a color developing device 6, and the photosensitive belt 1
Each color image is sequentially formed thereon.

The photosensitive belt 1 rotates in the direction of arrow A in the figure.
Each of the monochromatic image images formed thereon is synchronized with the photoreceptor belt 1 on an intermediate transfer belt 10 rotating in the direction of arrow B in FIG. Are sequentially superimposed and transferred by a predetermined transfer bias applied to the recording medium.

The yellow, cyan, magenta, and black images superimposed on the intermediate transfer belt 10 are fed from a paper supply table (paper supply cassette) 17 to a paper supply roller 18 and a conveyance roller pair 1.
The transfer roller 14 collectively transfers the transfer paper 17A onto the transfer paper 17A that has been conveyed to the transfer section via the registration rollers 9A and 19B and the registration roller pair 20A and 20B. After the transfer is completed, the transfer paper 17A is fixed by the fixing device 80 to complete a full-color image, and is discharged onto the discharge stack 82 via the pair of discharge rollers 81A and 81B.

In the figure, reference numeral 15 denotes a cleaning device including a cleaning member 15A which is always in contact with the photosensitive belt 1 and cleans toner on the photosensitive belt 1, and a waste toner collecting container. Belt 1
The cleaning blade 16A of the cleaning device 16 is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and after the formed image is transferred onto the transfer paper 17A, It is brought into contact with the surface of the transfer belt 10.

The waste toner scraped off from the intermediate transfer belt 10 by the cleaning blade 16A is removed by the auger 16B provided in the cleaning device 16.
The sheet is conveyed toward the front of the drawing, and further conveyed to a waste toner collecting container 15C by a conveying unit (not shown) provided on the front side of the process cartridge 31. By exchanging the process cartridge 31 when a predetermined amount or more of waste toner is stored in the waste toner collecting container 15C, the life of the process cartridge 31 can be extended.

Also, the photosensitive belt 1, the charging charger 4, the intermediate transfer belt 10, the cleaning devices 15 and 16
Are integrally formed as a process cartridge 31, and the waste toner collecting container 15 </ b> C is exchangeably incorporated into the process cartridge 31. The case exterior part on the side of the registration roller 20B of the process cartridge 31 also has a function as a paper conveyance guide.

Next, the structure of the image forming apparatus main body will be described with reference to FIG. The apparatus main body structure includes a main body frame 9 as an immovable portion housing and a front frame 8 as a front housing capable of opening a transfer path of the transfer paper 17A. The color developing device 6 and the process cartridge 31 are exchangeably arranged inside the main body, and the fixing device 80 is further arranged above the color developing device 6 and the process cartridge 31, and a paper discharge stack portion 82 is formed at the upper part of the main body.

The front frame 8 is supported so as to be openable and closable about a rotation support shaft 9A provided on the main body frame 9,
Normally, as shown in FIG. 1, the main body frame 9 is held in a closed state. The transfer paper 1 is placed in the transfer path of the transfer paper 17A.
When the jam of 7A occurs, the lock mechanism (not shown) for the front frame 8 is released, and the front frame 8 is released as shown in FIG. The front frame 8 includes a transport roller 19A and a registration roller 2 which constitute a part of the transfer paper transport path.
0A, the transfer roller 14 and the like are held, and by opening the front claim 8, the transfer paper transport path is exposed, so that the jam can be easily removed. At this time, the other image forming units are stationary, and no problems such as toner scattering and leakage occur.

FIG. 3 shows a one-component developing type color developing device 6 according to the present invention and a photosensitive belt 1 serving as an image carrier.
FIG. 4 is a relationship diagram of a bias application and control circuit, and shows, as an example, a case where the cyan developing unit 22 is at a developing position.

A non-magnetic toner T as a one-component developer is stored in the developing case 22C. The color developing device 6 has a state where a portion facing the photoreceptor belt 1 is open, and the photoreceptor belt 1 and the developing roller 23C are in contact with a predetermined nip width at the opening.
The developing roller 23 </ b> C is made of a material such as conductive rubber or metal, and is rotated in the same direction as the rotation direction of the photosensitive belt 1.

On the rear side of the developing roller 23C, there is provided a supply roller 25C for supplying the toner T in the developing case 22C to the developing roller 23C. The supply roller 25C
Rotates at a constant linear velocity ratio in the same direction as the developing roller 23C while contacting the developing roller 23C with a constant bite amount. For the supply roller 25C, a foam or the like is often used as an elastic body.

Further, a scraping member 27C is provided which is in contact with the supply roller 25C with a fixed bite amount so as to scrape the used toner T. Developing case 22C
Partitioning member 28C provided between and scraping member 27C
As a result, the powder pressure of the toner T applied to the contact portion between the developing roller 23C and the supply roller 25C is reduced.

The blade 26C, which is a thin layer member that regulates the amount of toner transported by the developing roller 23C and thins the toner T on the developing roller, is pressed against the developing roller 23C with a constant bite amount. Is provided.

A predetermined developing bias voltage is applied to the developing roller 23C from a developing bias power supply 40 as a first bias applying means, and a predetermined supply bias voltage is applied to the supply roller 25C from a supply bias power supply 44. You. The blade 26C is connected to a blade DC power supply 43 as a second bias applying means via a voltage variable device 42 as a variable bias control means.
A C bias voltage is applied. Further, a blade AC power supply 41, which is also a second bias applying means, supplies D
The AC component is superimposed on the C component.

These voltages are determined according to the values detected by the toner density sensor 50 in the color image forming apparatus shown in FIG. The toner concentration sensor 50, which is a one-component developer adhesion state detection unit, includes a light emitting diode (LED) and a light receiving element, and detects the amount of toner adhesion on the intermediate transfer belt 10. A grayscale batch pattern of each color is formed on the photoreceptor belt 1, and each voltage is determined so that a desired amount of toner adheres.

In this embodiment, the supply potential difference (developing bias voltage-supply bias voltage) is fixed to a voltage value at which the supply capability can be maintained so that the density does not decrease in a solid image. The blade potential difference (development bias voltage-supply bias voltage) can be varied by the voltage varying unit 42.

The toner T supplied onto the developing roller 23C by the supply roller 25C undergoes triboelectric charging with the developing roller 23C, and is conveyed toward the blade 26C by electrostatic force and physical force. The toner T on the developing port 23C is charged again by frictional charging while its passing amount is regulated by the blade 26C. The toner T after passing through the blade 26C is sufficiently charged, and a uniform toner layer is formed. In this embodiment, since the reversal development is performed using the negatively charged organic photosensitive belt 1, the toner T is negatively charged.

The passing amount and charge amount of the toner T by the blade 26C are considerably affected by the blade potential difference. Blade potential difference 1, Passage amount 1, Charge amount 1: V
bll, Ml, Ql, blade potential difference 2, passage amount 2, charge amount: Vbll <V in Vb12, M2, Q2
In the case of b12, Ml <M2 and Ql <Q2. In the initial toner having a good fluidity of the toner T, the larger the amount of the toner, the weaker the holding power of the toner T in the upper layer of the developing roller 23C, and there is a possibility that white drop due to a defective toner thin layer may occur.

FIG. 4 shows the relationship between the toner cohesion, the number of prints, and the white spot when the blade potential difference is fixed at Vb12. The degree of toner aggregation gradually increases, and
It is no longer occurring with sheets. Vbll the blade potential difference
And the amount of charge by the blade 26C is low, so that there is no margin for fogging over time.

Therefore, according to the present invention, as shown in the flowchart of FIG. 5, when printing is started, the number of prints is counted up to check the number of prints. To increase the blade potential difference.

In the color image forming apparatus shown in FIG. 1, the bias voltage of the developing device of each color of the color developing device 6 causes the photosensitive belt 1 to form a gray scale batch pattern of each color as described above, and the light emitting diode ( An amount of toner attached to the pattern on the intermediate transfer belt 10 is detected by a toner density sensor 50 including an LED (LED) and a light receiving element, and is determined so as to have a desired amount of attached toner.

FIG. 6 shows the normal state of the gray scale patch and the state in which white spots are generated.
0 is a detection result detected. In a normal state, the output value ripple Vr is small.
The output value decreases and the ripple Vr increases.

Therefore, the ripple at which white spots occur is represented by Vr
0, the ripple of the output value of the toner density sensor 50 is Vr,
Assuming that the blade potential difference at the time of toner adhesion adjustment is ΔVbl and the increase of the blade potential difference at one toner adhesion adjustment is α, the control shown in the flowchart of FIG. ) Is added to the toner adhesion amount adjustment software.

That is, in FIG. 7, when the counter is counted up by one (count value N), the writing of the gray scale pattern is started, the gray scale pattern is written, and the ripple Vr of the output value of the toner density sensor 50 is checked. Then, the blade potential difference is compared with the ripple Vr0 at which white drop occurs, and if Vr0> Vr, the blade potential difference is set to ΔVbl + (N−1) α; otherwise, the process returns to the beginning.

[0040]

According to the first aspect of the present invention, since the blade potential difference is variably controlled in accordance with the change in the degree of aggregation of the toner, it is possible to provide a good image without white spots over time.

According to the second aspect of the present invention, the relationship between the degree of aggregation of the toner over time, the number of latent image formations, and the occurrence of white spots is determined in advance, and the number of times the blade potential difference is changed is determined. , And a good image free of white spots can be provided with a simple configuration.

According to the third aspect of the present invention, the toner image is actually formed on the image carrier, and the white drop of the toner image is directly detected by the toner image adhesion state detecting means. And a good image can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of the entire inside of a color image forming apparatus including a color developing device according to the present invention, in which a front frame is closed with respect to a main body frame portion.

FIG. 2 is a schematic configuration diagram of a state where a front frame is opened with respect to the main body frame portion.

FIG. 3 is a diagram showing a relationship between a one-component developing type color developing device, a photoreceptor belt, and a bias application and control circuit according to the present invention.

FIG. 4 is a graph showing the relationship between the toner aggregation degree, the number of printed sheets, and white spots when the blade potential difference is fixed.

FIG. 5 is a flowchart of an operation for increasing a blade potential difference when the number of prints is equal to or greater than the number of prints.

FIG. 6 is a diagram illustrating a detection result obtained by detecting a normal state of a gray scale patch and a state in which white spots are generated by a toner density sensor.

FIG. 7 is a diagram showing a state in which a toner image is actually formed on a photosensitive belt;
9 is a flowchart of an operation of directly detecting a white drop of a toner image to determine a blade potential difference.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor belt (image carrier) 2 photoconductor belt rotation roller 3 photoconductor belt rotation roller 4 charging charger 5 laser writing unit 6 color developing device 8 front frame 9 main body frame 9A rotation support shaft 10 intermediate transfer Belt 11 Rotating roller of intermediate transfer belt 12 Rotating roller of intermediate transfer belt 13 Bias roller 14 Transfer roller 15 Waste toner collecting container 15A Photoconductor cleaning member 16 Intermediate transfer belt cleaning device 16A Intermediate transfer belt cleaning blade 16B Auger 17A Transfer Paper 18 Paper feed roller 19A / 19B Transport roller pair 20A / 20B Registration roller pair 22 Cyan developing unit 22C Developing case 23C Developing roller 25C Supply roller 26C Blade (thin layer member) 27C Scraping member 28C Retaining member 31 Process cartridge 40 Developing bias power supply (first bias applying means) 41 Blade AC power supply (second bias applying means) 42 Voltage variable device (bias variable control means) 43 Blade DC power supply (second bias applying means) ) 44 Supply bias power supply 50 Toner density sensor (one-component developer attached state detecting means) 80 Fixing device 81A / 81B paper discharge roller pair 82 paper discharge stack unit T Toner (one-component developer)

Claims (3)

[Claims] A developing roller for developing a latent image on the image carrier with a one-component developer carried on a surface of the developing roller; and a one-component developer on the developing roller. A developing device comprising: a thin member to be thinned; and first bias applying means for applying a predetermined developing bias voltage to the developing roller. A second bias application unit for applying a predetermined bias voltage so that a predetermined potential difference is generated, and a bias variable control unit for variably controlling the potential difference according to a change in the cohesion degree of the one-component developer. A developing device. 2. The developing device according to claim 1, wherein said variable bias control means variably controls said potential difference in accordance with the number of latent image formations on said image carrier. 3. A one-component developer adhesion state detecting means for forming a latent image as a measurement pattern on the image carrier, and detecting a one-component developer adhesion state on the latent image as the measurement pattern, 2. The developing device according to claim 1, wherein the variable bias control unit variably controls the potential difference according to a measurement result of the one-component developer adhesion state detecting unit.